Question

I have a data frame with two columns: an ID and some numeric value foo. I want to be able to get a vector of the IDs corresponding to foo values similar to the foo value of a given ID. Is there some easy way to do this in R?

Answer 1

I’ll assume you have a dataframe rather than a vector. Maybe something like this:

df <- data.frame(id = 1:10, foo = runif(10))
givenID <- 8
tolerance <- 0.2
subset(df, abs(foo - foo[id == givenID]) < tolerance)$id

It will include in the output the given ID, but you can get rid of that if you need to, wrap it in a function, etc.